1. Field of the Invention
The present invention relates to an improved diffraction optical element (DOE). In particular, it relates to the DOE having a smoothly etched surface substrate.
2. Description of the Prior Art
With the miniaturization of electronic components and electronic devices used in mobile telephones, personal computers, etc., there has been increasing demand for finer and higher speed drill processing. The application of a DOE has been promoted as a key device to satisfy this demand.
Unlike conventional optical components utilizing refraction and/or reflection, the DOE utilizes optical diffraction and directly controls the optical phases, and therefore, a wide range of applications including, multi-spot beam splitters, for example, can be expected.
As shown in FIG. 5, the DOE can split one processing laser beam into multiple spots. Simultaneous processing at plural spots, shaping patterns such as marking, and non-circular-shape processing have been achieved with high-speed.
FIG. 4 shows an example wherein the DOE is utilized in drill processing using a carbon dioxide gas laser to split one processing laser beam into multiple spots and simultaneously drill a plurality of holes. (Japanese Patent Laid-Open No. 2000-280226 and Japanese Patent Laid-Open No.2000-280225).
The present invention provides an improved DOE which has a smoothly etched surface.
The DOE of the present invention comprises a polycrystalline substrate which has an upper film layer having the same material as the substrate, and having finer polycrystalline grains than that of the substrate or having an amorphous phase laminated on the substrate.
It is preferable that the DOE be provided with a polycrystalline substrate whose diameter of crystal grains at an etched surface is not more than 1 xcexcm.
It is also preferable that the DOE be provided with an amorphous phase at an etched surface of the substrate.